Ravnica is a vast, worldwide cityscape—a patchwork of grand halls, decrepit slums, ancient ruins, and layer upon layer of stonework structures. Of the world's countless civic centers, one looms large above all others: the City of Ravnica, a metropolis so vast that its name has long since become synonymous with the entire plane. It is here, amid mazes of streets and towering gothic spires, that Ravnica's guilds vie for power and control.

Ravnica's guilds had been openly at war for centuries, each claiming dominion over the others. Then something began to happen that gave the guilds pause: The spirits of the dead were lingering in the world. The guild masters of old agreed to divert their energy toward investigating the phenomenon, leading to the signing of the Guildpact, the ancient accord that established relative peace on the plane.

Each of the ten guilds mastered two of the five colors of mana, and each had its own cultural identity and essential function.

Boros (red-white): The Boros Legion believed in a higher law—one in which righteousness is fire, and justice the light that shines from it. Led by the angel Razia, the Boros were Ravnica's most formidable military force, and the enforcers of its laws.

Selesnya (green-white): "Once you are with us, you are an equal among us. Until then, you are lost," said the wolfrider evangel Tolsimir, an agent of the Selesnya Conclave. The Conclave thought itself a selfless, nurturing, spiritual congregation, but others regarded it as a brainwashing nature cult.

Golgari (black-green): The Golgari believed you can't truly live until you die. With its vast horde of undead that served as both standing army and labor force, the Golgari operated in Ravnica's undercity, slowly taking over abandoned and derelict areas like a fetid slime mold.

Dimir (blue-black): House Dimir was so secretive that only some knew that it even existed. Over the millennia, ghost stories about the Dimir grew more and more complex, telling of ancient, undead necromancer-advisors, phantasmal assassins, and slick, black horrors slithering through the endless maze of sewers under the city.

Orzhov (white-black): To find the Orzhov, the saying went, follow the gold. The so-called Guild of Deals was a rigid hierarchy with the wealthy ghost-patriarchs ruling from the top and countless indentured servants forming the base. Holding this fragile social order in place was a veneer of religious pomp and ritual, though few believed the Orzhov worship any god other than coin.

Gruul (red-green): The Gruul Clans celebrated base urges and lived by instinct, considering all of civilization to be an elaborate cage that suppresses desire. Once a powerful guild, the Gruul were an assemblage of beggars, gangs, and raiding parties, with the largest of their gangs led by the cyclops Borborygmos.

Izzet (blue-red): The undisputed masters of spellcraft and invention on Ravnica, the Izzet were rabid inventors, fusing elemental magics with technology to power their creations. Led by the capricious and unfathomably brilliant dragon Niv-Mizzet, the Izzet magewrights endlessly created and destroyed, driven only by rabid passion for discovery.

Azorius (white-blue): The Azorius Senate was the primary origin of all laws on Ravnica. The Azorius believed that their rigid system of governance kept nearly everything on Ravnica running smoothly. Justice is blind, and that included the guild's venerable Grand Arbiter, Augustin IV, who some say was blind to Ravnica's most significant problems.

Rakdos (black-red): The Cult of Rakdos was a thrill-killing, pleasure-seeking cabal led by the ancient demon Rakdos. Even as a force of chaos, the Rakdos were a resource for the law-abiding guilds; when the denizens of Ravnica needed an obstacle removed or an unsavory client entertained, the minions of Rakdos were happy to oblige.

Simic (green-blue): Amidst the chaos of Ravnican politics and strife, the researchers of the Simic Combine worked industriously to improve their world. The Simic were charged with maintaining nature on Ravnica. In ever stranger ways, the Simic "modified" nature so it could survive on a world increasingly blanketed under civilization.